Direwolf does not need Flrig to run at all and especially since you're using a Signalink which takes care of the PTT signal within itself. Putting that another way, if the SIgnalink sound chip is told to play audio and if it's loud enough, it will assert PTT automatically. In theory, it makes things much simpler. Btw, even Fldigi doesn't need Flrig to run as it has many self-contained ways to control radios, etc. Flrig just exposes a lot more of the deeper controls of your radio to your computer.
For Direwolf and packet radio.. ignore Flrig. Not needed. Once you get Direwolf working with your Signalink and NO CAT connection, we can then consider looking at CAT controls which could give you other controls like frequency control, setting power levels, etc. but those are all OPTIONAL.